Geochemical Modeling Research Articles

Application of Hydrochemical Parameters as Tool for Sustainable Management of Water Supply Network

Effective management of Water Supply Systems (WSSs) is crucial for ensuring safe drinking water. The WSS of Varaždin County is a complex network involving three groundwater sources: Bartolovec and Vinokovščak wellfields (alluvial aquifers) and Bela karstic spring. To achieve a comprehensive characterization of WSSs, routine laboratory data was integrated with stable isotopes and geochemical modeling. Within this study, all measured parameters remain below the Maximum Contaminant Level (MCL), ensuring water safety for human consumption. The Piper diagram identified variations in water sources based on their chemical composition, providing a simplified overview of mixing patterns within WSSs. Among the modeling approaches, inverse modeling (IM) was found to be more reliable than forward modeling (FM) and mass balance modeling (BM). Despite the limited capacity of δ18O to provide accurate mixing results, it was revealed that the reservoir water was in equilibrium with the air (no evaporation effects), indicating well-sealed reservoirs. Mixing modeling showed that the western, southwestern, and northern parts of the WSS mixed all three sources, whereas the eastern and southeastern areas primarily relied on the deeper aquifer of the Bartolovec source, indicating potential vulnerability. Strict validation criteria ensured the reliability of results, demonstrating the effectiveness and applicability of geochemical modeling in water security management plans.

Water Quality Analysis and Risk Assessment of Potential Toxic Elements in Selected Surface Water Around Mining Sites in Abuakwa South Municipal, Ghana

ABSTRACTSurface water quality at Abuakwa South Municipal has received threats from surrounding mining communities, which are becoming a major concern to the public. As a result, this study aimed to assess water quality by examining the concentration of lead (Pb), cadmium (Cd), and zinc (Zn) pollution in surface water. Fifteen samples were obtained from surface water using a 1.5 L plastic bottle. The mean concentrations of Pb and Cd were above WHO guidelines of 0.01 and 0.003 mg/l, respectively, except for Zn which was below the stipulated limit of 3.0 mg/l. The geochemical process model shows that Cd, Pb, and Zn are adsorbing (released from the drainage to the surrounding environment) in sites 1 and 3 whereas Pb is desorbing (added to the drainage) in site 2. A hazard quotient greater than 1 was recorded for Cd in adults through the ingestion route of exposure at all the sites. Cancer risk also shows that the inhabitants are at risk through the ingestion route of exposure. The findings of this study suggest intake of water draining within the vicinity is unsafe and poses severe health risks.

Investigation of Scaling and Materials’ Performance in Simulated Geothermal Brine

Geothermal energy generation faces challenges in efficiency, partly due to restrictions on reinjection temperatures caused by scaling issues. Therefore, developing strategies to prevent scaling is critical. This study aims to simulate the scaling tendencies and corrosion effects of geothermal fluids on various construction materials used in scaling reactor/retention tank systems. A range of materials, including carbon steel, austenitic stainless steel, duplex stainless steel, two proprietary two-part epoxy coatings, and thermally sprayed aluminium (TSA), were tested in a simulated geothermal brine. Experiments were conducted in a laboratory vessel designed to replicate the wall shear stress conditions expected in a scaling reactor. The tests revealed varying scaling tendencies among the materials, with minimal corrosion observed. The dominant scale formed was calcium carbonate, consistent with geochemical modelling. The findings suggest that despite the high operating temperatures, the risk of corrosion remains low due to the brine’s low chloride content, while the wettability of materials after immersion may serve as a useful indicator for selecting those that promote scaling.

Alunite in Cross Crater, Mars: Evidence for a Possible Site of Ancient Life.

Cross Crater is a 65-km impact crater located in the Noachian highlands of the Terra Sirenum region of Mars. Geochemical modeling has indicated that alunite detected on the southwest wall of Cross Crater could have been formed by a fumarole upwelling into Cross Crater Lake and could indicate that an environment favorable to the development of life may have existed several billion years ago. Alunite did not form when Noachian precipitation reacted with basalt nor when the sediments and groundwater resulting from this reaction were reacted with a fumarole. Only when Cross Crater Lake water was equilibrated with sulfuric acid, thought to be a major component of the atmosphere in the Hesperian, following reaction with fumarole groundwater, did alunite precipitate from solution. Kaolinite, silica, or an Al-smectite such as montmorillonite also formed. The proximity of Cross Crater to the Tharsis volcanic region relative to Columbus crater, where alunite has also been detected, may have resulted in larger amounts of magmatic water input to the lake from sources along fractures that extend westward from Tharsis. This could explain the more extensive deposit of alunite at Cross Crater relative to Columbus crater.

Phase equilibrium constraints on the pre-eruptive conditions of alkaline basalts of the Main Ethiopian Rift and their bearing on the production of peralkaline rhyolites

Abstract Bimodal magmatism is characteristic of the geodynamic evolution of the Main Ethiopian Rift (MER), which is a reference area for the study of the processes leading to continental break-up before seafloor spreading. There are abundant emissions of basalts and rhyolites, which are in possible parent-daugther relationships. However, the P-T-H2O conditions of production and storage of the basaltic end member remain unclear. Crystallization experiments have been conducted on an alkali basalt from the MER to define its pre-eruptive conditions and shed light on the compositional evolution of derivative liquids and source conditions. The experiments were performed at 100-200 MPa, 975-1080°C, varying H2O/CO2 ratios, corresponding to melt water contents of 1-5 wt%, at fO2 slightly lower than the Fayalite-Magnetite-Quartz (FMQ) solid buffer. Comparison between the petrological attributes of the starting rock and the experiments shows that the basaltic magma was stored at 150-200 MPa, 1050 ± 10°C, with 1-2 wt% H2O in melt, with fO2 near FMQ prior to eruption. Geochemical modelling shows that the corresponding mantle source contained about 0.1 wt% H2O, reflecting a metasomatized source. Extensive crystallization of such basalts produces SiO2-rich liquids, which are not yet peralkaline, however. This underscores that extreme fractionation (>90 wt%) is required in order to produce peralkaline derivatives from mildly alkaline basalts. This extreme fractionation and the water-rich nature of the starting basalt readily explain the H2O-rich condition of peralkaline rhyolites that have fueled caldera forming eruptions in the Rift.

Controls of low injectivity caused by interaction of reservoir and clogging processes in a sedimentary geothermal aquifer (Mezőberény, Hungary)

Low injectivity is often experienced in geothermal doublets installed in sandstone reservoirs. This even led to a shutdown of the Mezőberény (Hungary) geothermal site. An on-site campaign was carried out in January 2021 to prepare a stimulation aiming to enhance the transmissivity of the sedimentary reservoir and the near-wellbore zone of this site. Previous studies have concluded that insufficient injectivity may be linked to a high skin effect in the near well-bore zone and pore clogging in combination with the low net sandstone content of the fluvio-deltaic reservoir. A chemical soft stimulation based on the injection of hydrochloric acid (HCl) was successfully used to unclog and recover the well injectivity. Despite such empirical evidence, the geochemical mechanisms leading to both, detrimental formation of clogging and the HCl-driven transmissivity restoration, have not yet been elucidated. This work presents the results of a novel analysis aiming at (a) predicting the dominant type of clogging forming in the near-well bore zone; (b) quantifying the drop in hydraulic conductivity as clogging occurs; and (c) supporting the optimization of the HCl dosage during the chemical soft stimulation. The study is supported by new experimental datasets never presented before from the Mezőberény site and a geochemical model set-up simulating the main mechanisms involved in the clogging and unclogging processes. It is concluded that the biofilm formation was the dominant, while the precipitation of calcite and amorphous ferrihydrite—later reduced to magnetite by microbes—was the secondary clogging mechanism: In the long-term (yearly scale) simulating the hydraulic conductivity showed a decline with forming scales; therefore, biofilm was presumably responsible for the experienced rapid (1 month) clogging. When modelling the chemical stimulation, the estimated amount of precipitated minerals was dissolved already with 2.5 mol of HCl per liter of water (~ 10 m/m%). Therefore, the 20 m/m% of HCl chosen during the field campaign might had a beneficial effect dissolving the potentially higher amount of scaling and/or the carbonate minerals of the matrix near the wellbore. Overall, it is concluded that the chemical and the microbial analyses together with the geochemical model were critical to tailor the remediation attempts and to propose further development or reconstruction of the surface system before going into operation to prevent recurrent impairments. Our findings highlight the importance of interactions of various clogging mechanisms with each other as well as with the reservoir processes and provide approaches to tackle the issue of injectivity drop by characterizing and quantifying their effects.

Local hydroclimate alters interpretation of speleothem δ18O records

Oxygen isotopes (δ18O) are the most commonly utilized speleothem proxy and have provided many foundational records of paleoclimate. Thus, understanding processes affecting speleothem δ18O is crucial. Yet, prior calcite precipitation (PCP), a process driven by local hydrology, is a widely ignored control of speleothem δ18O. Here we investigate the effects of PCP on a stalagmite δ18O record from central Vietnam, spanning 45 – 4 ka. We employ a geochemical model that utilizes speleothem Mg/Ca and cave monitoring data to correct the δ18O record for PCP effects. The resulting record exhibits improved agreement with regional speleothem δ18O records and climate model simulations, suggesting that the corrected record more accurately reflects precipitation δ18O (δ18Op). Without considering PCP, our interpretations of the δ18O record would have been misleading. To avoid misinterpretations of speleothem δ18O, our results emphasize the necessity of considering PCP as a significant driver of speleothem δ18O.

Crustal melting and continent uplift by mafic underplating at convergent boundaries.

The thick crust of the southern Tibetan and central Andean plateaus includes high-conductivity, low-velocity zones ascribed to partial melt. The melt origin and effect on plateau uplift remain speculative, in particular if plateau uplift happens before continental collision. The East Anatolian Plateau (EAP) has experienced similar, more recent uplift but its structure is largely unknown. Here we present an 80 km deep geophysical model across EAP, constrained by seismic receiver functions integrated with interpretation of gravity data and seismic tomographic, magnetotelluric, geothermal, and geochemical models. The results indicate a 20 km thick lower crustal layer and a 10 km thick mid-crustal layer, which both contain pockets of partial melt. We explain plateau uplift by isostatic equilibration following magmatism associated with roll-back and break-off of the Neo-Tethys slab. Our results suggest that crustal thickening by felsic melt and mafic underplate are important for plateau uplift in the EAP, Andes and Tibet.

Geochemical modeling of U-Ni-Co-As transport and deposition in acidic basinal brines: Implications for unconformity-related U-(Ni-Co-As) mineralization in the Athabasca Basin (Canada)

The unconformity-related uranium (URU) deposits, which are best developed in the Proterozoic Athabasca Basin (Canada), can be divided into the monometallic (U) and polymetallic (U-Ni-Co-As) subtypes. Different models have been proposed to explain the formation of the two subtypes of URU deposits. The conventional “diagenetic-hydrothermal” model suggests that both subtypes formed from oxidizing, acidic basinal brines in a unified mineralization system, whereas a newly proposed model suggests that the polymetallic deposits formed from monometallic U deposits superimposed by Ni-Co-As mineralization. While the second model has been the subject of ongoing debates, there are also unanswered questions in the diagenetic-hydrothermal model; in particular, it remains unclear what geological factors controlled the formation of one subtype or another in a unified mineralization system. This paper aims to address this question with geochemical modeling of hydrothermal U-Ni-Co-As transport and deposition using the Geochemist's Workbench (GWB) software. The conditions for U-Ni-Co-As transport were examined with thermodynamic modeling. The results indicate that highly oxidizing (log fO2(g) > −25), acidic (pH = 3.5) brines can transport large amounts (>100 ppm) of U together with Ni-Co-As, whereas moderately oxidizing (−40 < log fO2(g) < −25), less acidic (3.5 < pH < 6) brines can transport only minor amounts (<1 ppm) of U while still capable of carrying large amounts (>100 ppm) of Ni-Co-As, and very reducing (log fO2(g) < −40) brines with pH from 3.5 to 6 can dissolve only minor amounts (<1 ppm) of U and Ni-Co-As. The mechanisms of U-Ni-Co-As deposition were examined with reaction path modeling involving fluid-rock interaction and fluid-fluid mixing. The results indicate that as a U-Ni-Co-As-bearing, acidic, oxidizing brine progressively reacts with basement rocks or mixes with a reducing fluid, U precipitates before Ni-Co-As in relation to pH increase and fO2(g) decrease. In the case of fluid mixing, while U precipitation can be caused by any of the reducing agents (CH4(aq), H2(aq), H2S(aq), and Fe2+(aq)) in the reducing fluids examined, Ni-Co-As deposition requires the participation of CH4(aq) or H2(aq). Based on the modeling results, it is inferred that U and Ni-Co-As were not transported by the same fluid, otherwise all the URU deposits would be polymetallic. The U was most likely derived from the basin rather than from the basement, because as oxidizing basinal brines infiltrate and interact with basement rocks, their ability to dissolve and transport U quickly diminishes due to fO2(g) decrease and pH increase. In contrast, as these basinal brines infiltrate the upper part of the basement, which is moderately oxidizing, they retain the ability to dissolve and transport significant amounts of Ni-Co-As, enabling the scavenging of these metals from the basement. While all URU mineralization requires U-bearing basinal brines and reducing agents, the formation of polymetallic (U-Ni-Co-As) deposits depends on the availability of Ni-Co-As-rich lithologies in the upper part of the basement, together with an ample supply of robust reducing agents, such as CH4 and H2 that were derived from the deeper part of the basement. Therefore, although the possibility that polymetallic U-Ni-Co-As deposits formed from Ni-Co-As mineralization superimposing on monometallic U deposits cannot be ruled out, the results of this study demonstrate that both polymetallic and monometallic URU deposits can be formed in a unified diagenetic-hydrothermal mineralization system in the Athabasca Basin.

The Contribution of Carbonaceous Material to Gold Mineralization in the Huangjindong Deposit, Central Jiangnan Orogen, China

The Huangjindong gold deposit in northeastern Hunan is one of the most representative gold deposits in the Jiangnan Orogenic Belt. The orebodies are mainly hosted in the Neoproterozoic Lengjiaxi Group, which comprises carbonaceous slates. Abundant carbonaceous material (CM) can be found in the host rocks and ore-bearing quartz veins, but its geological characteristics and genesis, as well as its association with gold mineralization, are still unclear. Systematic petrographic observation demonstrated two types of CM in host rocks and ores, i.e., CM1 and CM2. Among them, CM1 is the predominant type and mainly occurs in the layered carbonaceous slates, while CM2 is mostly present in quartz veins and mineralized host rocks. Laser Raman spectroscopic analyses of CM1 were performed at higher temperatures (376–504 °C), and CM2 was generated at similar temperatures (255–435 °C) to gold mineralization. Combined with previous studies, we can conclude that CM1 was produced by Neoproterozoic to early Paleozoic metamorphism before gold mineralization, while CM2 is of hydrothermal origin. Geochemical modeling indicates that CM1 could promote gold precipitation through reduction, as well as facilitate structure deformation and metal absorption as previously proposed. However, hydrothermal CM2 is favorable for gold mineralization because it triggers sulfidation, similar to other Fe-bearing minerals (such as siderite) in the host rocks. Consequently, both types of CM in the Huangjindong deposit are favorable for gold mineralization and carbonaceous slates could be important gold-bearing units for future ore prospecting in the Jiangnan Orogen as well as other places in South China.

Characterization and solubility measurement of synthetic uranophane and sklodowskite under oxic groundwater conditions

Naturally occurring uranyl silicates can serve as solubility-limiting solid phases (SLSPs) of U(VI) in the oxic environment of granitic groundwater, which is likely to occur in crystalline host rock media in Korea. In this study, two synthetic uranyl silicates, uranophane (Ca[UO2SiO3OH]2·5H2O) and sklodowskite (Mg[UO2SiO3OH]2·6H2O) were prepared and used to measure the U(VI) solubility in simulated groundwater (sGW), mimicking the composition of samples collected from the underground research tunnel at the Korea Atomic Energy Research Institute (KAERI). The solid- and solution-phase species involved were examined in detail using various characterization methods. According to the powder X-ray diffraction pattern and elemental analysis results, the synthetic mineral phases, which were identified as uranophane-α and sklodowskite having layered crystal structures, were retained intact in sGW; however, in 0.1 M NaClO4, emergence of other solid phases was observed. Enhanced FTIR and Raman spectroscopic data, particularly in the regions of 790–860 and 940–1020 cm−1 for the UO22+ and SiO44− ions, respectively, enable monitoring the changes in the solid phases. Ternary Ca–U(VI)-tricarbonato complexes were identified as the dominant dissolved U(VI) species in sGW using time-resolved laser-induced luminescence spectroscopy. Furthermore, the solubility constant of uranophane was calculated (log Ks,0° = 10.3 ± 0.4) and compared with the predicted values based on our geochemical modeling analysis and previously reported ones.

Groundwater geochemistry using modified integrated water quality index (IWQI) and health indices with special emphasis on nitrates and heavy metals in southern parts of Tirupati, South India.

Groundwater is particularly vulnerable to pollution in places with a high population density and extensive human usage of the land, especially in southern parts of Tirupati, India. To assess this, 60 bore-well samples were obtained and assessed for physical specifications, ion chemistry, and heavy metals during the pre- and post-monsoon seasons 2022. The current investigation employed a modified integrated water quality index (IWQI), conventional graphical and human health risk assessment (HHRA) of nitrates and heavy metals to know the groundwater chemistry and its detrimental health effects on humans. The major ions were analyzed using American public health association (APHA)standards, whereas heavy metals were analyzed using inductively coupled plasma optical emission spectrometry(ICP-OES). Additionally, pH Redox Equilibrium and C (PHREEQC),a geochemical model written in C programming language was employed to determine the saturation indices of mineral facies and ArcGIS 10.3.1 was used for spatial distribution patterns of IWQI. Then, the HHRA of nitrates and heavy metals was performed using United States environmental protection agency (USEPA)guidelines. The noteworthy outcomes include elevated levels of Ca2+, Mg2+, Cl-, NO3-, Cu,Fe, Mn, and Pb, demonstrating rock-water interaction, silicate weathering, Ca-Mg-HCO3 followed by mixed water facies, dissolution/precipitation, reverse exchange, and anthropogenic contamination are the major controlling processes in groundwater of southern Tirupati, India. The modified IWQI reveals that most groundwater samples (38%) fall under the bad quality class, with (47%) in the poor quality class and only (15%) classified as medium qualityclass in pre- and post-monsoon seasons. Elevated IWQI were observed in all directions except in the east, which is suitable for drinking. Moreover, the major hazard quotient (HQ) and hazard index (HI)for nitrates (NO3-) and heavy metals like copper(Cu), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn) are above the critical value of 1, revealing potential risk to humans, especially infants, followed by children and adults, entailing the instantaneous implementation of proper remedial measures and stringent policies to reduce the risk associated with groundwater pollution in the southern parts of Tirupati.

Dynamic evolution of the transcrustal plumbing system in Large Igneous Provinces: Geochemical and microstructural insights from glomerocrysts and melt inclusions

Abstract The nature of the magma plumbing system of Large Igneous Provinces is still poorly understood. Among these exceptional magmatic events from Earth’s past, the end-Triassic Central Atlantic Magmatic Province (CAMP) and the end-Cretaceous Deccan Traps (Deccan) coincided in time with two of the most catastrophic biotic crises during the Phanerozoic. In order to constrain the architecture of their magma plumbing system, glomerocrysts containing abundant bubble-bearing melt inclusions from basaltic lava flows of both CAMP and Deccan were investigated via in situ geochemical and microstructural analyses. The analysed glomerocrysts, dominated by augitic clinopyroxene crystals, represent fragments of a crystal mush entrained by basaltic magmas before eruption. The analysed melt inclusions, consisting of an intermediate to felsic composition glass and CO2-bearing bubbles, represent relics of interstitial melts and fluids within a porous crystal framework forming the crystal mush. The different volume proportions between bubbles and whole inclusions reveal that melt entrapment occurred after volatile exsolution. The minimum observed bubble/inclusion fraction indicates that the CO2 concentration in CAMP and Deccan melts was at least 0.3 wt.%, consistent with a maximum entrapment pressure of about 0.5 GPa at CO2–H2O fluid-saturated conditions. The MgO-rich composition of host clinopyroxene crystals and whole rocks is in contrast with the SiO2-rich composition of (trachy-) andesitic to rhyolitic glass of melt inclusions, pointing to disequilibrium conditions. Thermodynamic and geochemical modelling shows that fractional crystallization alone cannot explain the evolved composition of glass in melt inclusions starting from their whole rock composition. On one side, the oxygen isotope composition of clinopyroxene crystals in glomerocrysts ranges from + 3.9 (± 0.3) to + 5.8 (± 0.3) ‰ and their sample-averaged oxygen isotope composition spans from + 4.4 (N = 10) to + 5.6 (N = 10) ‰, implying that glomerocrysts crystallized from mafic melts with normal (i.e., mantle-like) to slightly low δ18O values. On the other side, the oxygen isotope composition of glass in melt inclusions ranges from + 5.5 (± 0.4) to + 22.1 (± 0.4) ‰, implying that melt inclusions entrapped intermediate to felsic melts with normal (i.e., mantle-like) to extremely high δ18O values, typical of (meta-) sedimentary rocks. Some melt inclusions are compatible with fractionation from the same mafic melts that crystallized their host mineral phase, but most melt inclusions are compatible with variable degrees of crustal assimilation and partial mixing, potentially followed by minor post-entrapment isotope re-equilibration. In the CAMP, where sedimentary basins are abundant, (meta-) pelites and occasionally granitoids were the most likely assimilants. On the contrary, in the Deccan, where sedimentary basins are rare, granitoids and metapelites were the most likely assimilants. Oxygen isotope compositions of glass in melt inclusions, spanning from mantle-like to crust-dominated signatures, suggest that the CO2 within their coexisting bubbles likely derived partly from the mantle and partly from assimilated crustal materials. The investigated glomerocrysts and their bubble-bearing melt inclusions are relics of a multiphase (i.e., solid + liquid + gas phases) crystal mush revealing a dynamic evolution for the magma plumbing system of both CAMP and Deccan, where crystals, silicate melts and exsolved fluids coexisted and interacted through most of the transcrustal section.

Source apportionment of Cd in karst soil based on the delayed geochemical hazard model.

Soil Cd contamination has become increasingly prominent in karst regions. Studies have generally elucidated the natural sources of Cd in high-background areas and analyzed their migration and enrichment mechanisms. This study comprehensively analyzed the total content and speciation of Cd in high-background areas using the delayed geochemical hazard (DGH) model to identify the sources of Cd in the region. The results indicated that Cd in the research area followed a pattern of gradual geochemical disasters. In Quaternary soil, brick-red soil, and submergenic paddy soil with hydromorphic characteristics, 32%, 7.69%, and 30% of soil Cd samples exceeded the critical threshold of the releasable total amount, respectively. Based on the DGH model, it was concluded that Cd in this region was mainly influenced by human activities. Field investigations corroborated this conclusion and aligned with the findings. Compared with the traditional source apportionment receptor models (mainly PCA and PMF), the DGH model not only saved considerable time and cost, but also avoided uncertainty associated with the results and complex and varied data processing and computational analysis processes. Moreover, the DGH model was able to identify the factors having the greatest impact on the ecological risk of Cd in the research area, thus facilitating targeted prevention and management planning based on the characteristics or chemical properties of their elements.

Geochemical modeling of diagenetic reactions between albitization of K-feldspar and plagioclase feldspar in sandstone reservoirs under the influence of CO2 partial pressure

Diagenetic albitization has been observed in sedimentary basins around the world. This process significantly changes the original composition of sandstones and the chemistry of the formation waters under the influence of partial pressure of CO2. The transformation of detrital feldspars into albite is considered a crucial diagenetic process in the Gulf Coast and North Sea reservoirs. Earlier studies suggest that plagioclase albitization typically happens before that of K-feldspar. In the Gulf Coast's Frio Sandstone, located in the Upper Oligocene at depths between 900 and 2400 m, detrital plagioclase is often dissolved and replaced by albite, while K-feldspar mostly dissolves without much substitution. Similarly, in the North Sea reservoirs, especially in the upper section of the Upper Triassic Lunde Formation at depths beyond 2900 m, plagioclase tends to undergo albitization, whereas K-feldspar remains largely unaffected or experiences minimal transformation. This research focuses on analyzing the differences in the albitization patterns of detrital and K-feldspar plagioclase through the KINDISP and Geochemist's Workbench (GWB) geochemical modeling tools, aiming to compare them. These diagenetic processes are crucial for reservoir geology, as they influence the concentration of silica in water, which, in turn, affects quartz cementation. This study aims to explore the variations in the albitization behavior of detrital and K-feldspar plagioclase using the KINDISP and Geochemist's Workbench (GWB) geochemical models and conduct a comparative analysis between them. Understanding these diagenetic reactions becomes relevant for reservoir geology analysis, as such phenomena control the aqueous silica concentration to some extent, which is consequently reflected in the quartz cementation. The dissolution of plagioclase and K-feldspar releases silica into the pore fluids. As the concentration of silica in the fluid increases, it leads to the precipitation of quartz as overgrowths on detrital quartz grains, a process known as quartz cementation. This was observed particularly in simulations involving temperature increases up to 150 °C, where the equilibrium between albite and anorthite was closely linked to the stability of quartz (Ben et al., 1993). The removal of feldspar through albitization reduces porosity and permeability but contributes silica to the system, which promotes quartz cementation. This, in turn, decreases the reservoir quality by filling pore spaces with secondary quartz, reducing the rock's ability to store and transmit fluids. Thus, the study highlights the importance of these diagenetic processes in reservoir evaluation, as the balance between feldspar dissolution and quartz cementation ultimately controls reservoir properties.

Effect of clayey sediment compression on fluoride enrichment in the Quaternary groundwater system of Cangzhou Plain, China

The effect of clay layer compression on the enrichment of groundwater fluoride remains unknown. Quaternary groundwater with high fluoride levels at the Cangzhou Plain, which has a long history of land subsidence caused by clay layer compression, poses a potential health risk. The spatial distribution and enrichment mechanisms of groundwater fluoride are identified by sample collection, hydrochemical analysis, and geochemical inverse modeling. The results revealed that fluoride concentrations in 82 % of the 122 groundwater samples above the limit in drinking water as 1.0 mg/L in China. Fluoride in shallow groundwater (depth <20 m, ∼average = 2.08 mg/L) was mainly originated from fluorite dissolution and influenced by groundwater HCO3−, pH, and cation exchange levels. Below ∼200 m, the main source of groundwater fluoride (∼average = 3.12 mg/L) was the compression−release of clay pore water with high F− concentration, which was generated by complex water-rock interaction. Based on hydrochemical inverse simulation and end-member mixing models, the pore water released from clayey sediments supplied 53 %−56 % of deep groundwater (>200 m) and contributed 2.07 −2.87 mg/L to F− concentration. The findings of this study provide a theoretical basis for future research on prevention of high fluoride groundwater induced by clayey sediment compression.

Tantalum in hydrothermal fluids

Understanding the behaviour of tantalum (Ta) in hydrothermal systems is pivotal for understanding its geochemical enrichment processes and economic extraction via hydrometallurgy. Yet, its behaviour in hydrothermal systems remains poorly characterised. This study investigates the coordination chemistry, speciation, and solubility of pentavalent Ta(V) in fluoride (F) − and chloride (Cl) −rich hydrothermal solutions up to 413 °C and 800 bar, utilising in-situ High Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy (HERFD-XAS). The results reveal the stability of high order fluoridotantalate complexes in fluoride-rich fluids solutions up to the highest investigated temperature, highlighting fluoride’s paramount role in enhancing Ta solubility through the formation of stable complexes in aqueous solutions. A transition from nonafluoridotantalate tetraanion (TaF94−) to heptafluoridotantalate dianion (TaF72−) complexes was observed as a function of temperature in solutions containing ≥1 m fluoride. Conversely, our findings indicate a negligible role for chloride in Ta complexation even in high Cl (∼6 m) aqueous solutions, suggesting that Ta chloride complexes do not contribute significantly to Ta transport in hydrothermal systems. Existing solubility data were reinterpreted based on an updated speciation model that integrates the in-situ XAS results. This confirms that Ta(OH)5(aq) predominates in solutions containing <0.02 m fluoride; oxyfluoridotantalate anions such as [TaF3(OH)3−] dominate in solutions containing intermediate fluoride concentrations (0.02–1 m), and the fluoridotantalate anions [TaF94− to TaF72−] occur in more concentrated fluoride solutions (>1 m) at hydrothermal conditions (∼100–400 °C). Derived thermodynamic data for these species enable better understanding and geochemical modelling of Ta transport in hydrothermal fluids, highlighting the potential of F-rich fluids to transport significant amounts of Ta.

How does the coupled action of freeze - Thaw and acidification affect the release of toxic elements from indigenous Zn smelting slags?

Under complicated field conditions, such as the coupled effects of freeze - thaw cycles (FTs) and acidification, the leaching behavior of potentially toxic element (PTEs) from indigenous Zn smelting slags (ZSS) was intricately connected to the mineralogy (e.g., the composition, assemblage, microstructure of mineral particles). In this study, FTs tests were carried out to explore the interactions between PTEs release and ZSS mineralogy. Subsequently, advanced characterization techniques were adopted to quantify the mineralogy and microstructure of ZSS. The results indicated that ZSS were mainly composed of silicate minerals (e.g., quartz, biotite and chlorite) and secondary Fe (III) oxyhydroxides (e.g., magnetite and limonite), accounting for 67.48% and 24.23%, respectively. The occurrence mode analysis revealed that 81.95% of As, 21.31% of Pb and 7.77% of Zn were hosted in limonite. About 37.89%, 59.34% and 34.50% of Cd, Pb and Zn were associated with carbonate bound fractions. Under FTs interacting with different pH conditions, the leaching concentrations of As, Cd, Cu, Pb and Zn did not significantly increase with the increase in FTs and pH. The microstructure damage of mineral particles in ZSS with the higher porosity was caused by both FTs and proton corrosion. More importantly, the geochemical modeling results suggested that the precipitation of hematite and magnetite might have little impacts on PTEs release under FTs and FTs with acidification. This work would provide a deeper understanding of PTEs release from smelting waste slags under complex physicochemical interactions.

Mobilization mechanisms and spatial distribution of arsenic in groundwater of western Bangladesh: Evaluating water quality and health risk using EWQI and Monte Carlo simulation

Arsenic (As) contamination in groundwater is emerging as a significant global concern, posing serious risks to the safety of drinking water and public health. To understand the release mechanisms, mobilization processes, spatial distribution, and probabilistic health risks of As in western Bangladesh, forty-seven samples were collected and analyzed using an atomic absorption spectrometer (AAS). The As concentrations in groundwater ranged from 1.97 to 697.4 μg L⁻1 (mean: 229.9), significantly exceeding recommended levels. The dominant hydrochemistry of As-enriched groundwater was Ca–Mg–HCO₃, with the primary sources of arsenic in groundwater being the dissolution of arsenic-bearing minerals in sediment and the recharge of aquifers from the Ganges River Basin. The assessment using the Entropy Water Quality Index revealed that the groundwater is unsuitable for drinking, with 89.36% (n = 42) of the samples surpassing the WHO's limit for arsenic. Rock-water interactions, including calcite dissolution and silicate weathering within the confined aquifer, predominantly influenced hydrochemical properties. The significant relationships among Fe, Mn, and As indicate that the reductive dissolution of FeOOH and/or MnOOH considerably contributes to the release of As from sediment into groundwater. Geochemical modeling analysis revealed that siderite and rhodochrosite precipitate into aquifer solids, suggesting a weak to moderate relationship among As, Fe, and Mn. The long residence time of groundwater, combined with the presence of a clayey aquitard, likely controls the mobilization of arsenic in the aquifer. For the first time, Monte Carlo simulations have been used in arsenic-prone areas to assess the severity of arsenic contamination in western Bangladesh. The analysis indicates that out of 100,000 people, 10 may develop cancer as a result of drinking arsenic-contaminated water, with children being more susceptible than adults.

Leaching and geochemical modeling of asbestos-cement waste and mine asbestos

Asbestos-Containing Materials (ACMs) were widely used in the construction sector but, due to their harmful health effects, many countries have banned their use. ACMs are classified as hazardous and, in contact with water, produce potentially harmful leachates. The objective of this work was to determine the leaching behavior of 20 elements from two asbestos-cement materials and mine asbestos samples across the entire pH range and varying liquid-to-solid ratios (column tests). The pH-dependence tests showed consistent leaching patterns across the three materials. Geochemical speciation model (LeachXS) predictions were successful in most cases of the batch experiments and were improved by adjusting iron oxides concentration for some elements. Model predictions were successful for fewer elements in the column experiments. Depending on the pH, element release was controlled by respective solid phase dissolution, sorption onto iron oxides and substitution in ettringite. Some leaching concentrations exceeded the EU limits for granular non-hazardous waste landfills. Considering the strongly alkaline nature of monolithic asbestos-cement waste undergoing carbonation, we propose all three materials to be disposed of in non-hazardous waste landfills, according to EU legislation. A case study concluded that geochemical modeling of ACMs leaching is a useful tool in estimating element release under various environmental conditions.